The present invention relates to a nanoparticle dispersed structure that is useful as an optical functional material, and to a method for manufacturing this structure. More particularly, it relates to a nanoparticle dispersed structure in which nanoparticles of a substance selected from among metals, metal compounds, and semiconductors are dispersed in a crosslinked polymer, and to a method for manufacturing this structure.
Because they exhibit nonlinear optical effects, metal and semiconductor particles whose size is on the order of nanometers are dispersed in glass or polymers to produce nanoparticle dispersions, which have been attracting attention as optical functional materials. Known methods for dispersing nanometer-sized particles in a matrix include 1) a method in which nanometer-sized metal particles and semiconductor particles are produced by sputtering, CVD, or another vapor phase method, and the surroundings thereof are covered with an inert substance such as silica to form a deposited film on a substrate (e.g., Japanese Laid-Open Patent Application H10-292065), 2) a method in which nanoparticles are dispersed and compounded in the liquid phase in a sol-gel compound (Japanese Laid-Open Patent Application H8-245263), 3) a method in which a semiconductor component is dispersed in a polymer, after which another component is diffused into this, and this product is irradiated with a laser to form nanoparticles (Japanese Laid-Open Patent Application H10-36517), and 4) a method in which various types of nanoparticles are deposited on a polymer resin in a thermodynamically unstable state, after which this is heated to change the polymer into a thermally stable state and diffuse the nanoparticles into the polymer (Japanese Laid-Open Patent Application H6-157771). 5) Another method has been discovered in which a monomer film capable of undergoing ring-opening polymerization is formed, over which a nanoparticle film is formed, after which this product is heated to effect polymerization and diffuse the nanoparticles into the polymer film (Japanese Laid-Open Patent Application H11-147958).
While sol-gel compounds do offer the valuable benefit of allowing manufacture in the liquid phase, it is generally held that their molding workability is poor, and that the dispersed particles are unstable and tend to clump into secondary particles. When a thermoplastic polymer is used as the dispersion medium, not only does this require sophisticated technology for precipitating particles on the surface while maintaining an unstable state, and diffusing these particles in the process stabilizing the polymer, but it is also well known that these particles tend to form secondary particles in the polymer. It is commonly held that a polymer with a three-dimensionally crosslinked structure has better dispersion stability than a linear thermoplastic polymer. Also, since nanoparticle dispersed structures are attracting attention for their optical functions, such as in materials for nonlinear optical elements, it is clear that optical transparency is an important characteristic desired of the dispersion medium material. Theories pertaining to the optical effects exhibited by nanoparticles suggest that the dielectric constant of the medium affects the characteristics of the nanoparticles.
It is an object of the present invention to provide a nanoparticle dispersion featuring a polymer having a crosslinked structure that is chemically inert with respect to the nanoparticles and that is effective in suppressing diffusion, and to provide a method for manufacturing this nanoparticle dispersion.
The present invention provides a nanoparticle dispersed structure, characterized in that nanoparticles of a substance selected from among (i) metals, (ii) metal compounds, and (iii) semiconductors are dispersed in a crosslinked polymer.
The present invention also provides a method for manufacturing a nanoparticle dispersed structure, characterized in that nanoparticles of a substance selected from among (i) metals, (ii) metal compounds, and (iii) semiconductors are deposited on a solid composed of a polymer precursor having a crosslinkable structure, after which said polymer precursor is crosslinked and the nanoparticles are dispersed in the crosslinked polymer by heating.
The present invention also provides a laminate of a nanoparticle dispersed structure, produced by the lamination of the above-mentioned nanoparticle dispersed structure.
The present invention further provides a laminate of a nanoparticle dispersed structure, characterized in that a laminate is manufactured by subjecting the above-mentioned nanoparticle dispersed structure at least once to a lamination process comprising the steps of (A) forming a solid film composed of a polymer precursor having a crosslinkable structure and (B) then depositing a substance selected from among (i) metals, (ii) metal compounds, and (iii) semiconductors on said solid film, and then crosslinking said polymer precursor and dispersing the nanoparticles in the crosslinked polymer by heating so as to form a layer composed of a nanoparticle dispersed structure.